Journal of Organic Chemistry
Journal of Organic Chemistry
5 years ago

Asymmetric Synthesis of Amino-Bis-Pyrazolone Derivatives via an Organocatalytic Mannich Reaction

Asymmetric Synthesis of Amino-Bis-Pyrazolone Derivatives via an Organocatalytic Mannich Reaction
Kari Rissanen, Suruchi Mahajan, Uğur Kaya, Pankaj Chauhan, Anssi Peuronen, Dieter Enders
A new series of N-Boc ketimines derived from pyrazolin-5-ones have been used as electrophiles in asymmetric Mannich reactions with pyrazolones. The amino-bis-pyrazolone products are obtained in excellent yields and stereoselectivities by employing a very low loading of 1 mol % of a bifunctional squaramide organocatalyst. Depending on the substitution at position 4 of the pyrazolones, the new protocol allows for the generation of one or two tetrasubstituted stereocenters, including a one-pot version combing the Mannich reaction with a base-mediated halogenation.

Publisher URL: http://dx.doi.org/10.1021/acs.joc.7b01113

DOI: 10.1021/acs.joc.7b01113

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